The present invention relates to a three-dimensional joint structure, formed by two hollow profiles, of a support frame for vehicles, and a method for its manufacture.
Joint structures for vehicle support frames are known in different embodiments. A three-dimensional joint, structure having a connecting part for connecting elements of a vehicle support frame is described in EP 0568 213 B1. The connecting part comprises a preferably extruded U-profile having two side plates and a web plate which connects the side plates, in which a support element is laid and bonded thereto through gluing. Essentially cuboid attachment parts are attached to the outsides of one side plate and the web plate, on whose faces further support elements may be placed and glued to the connecting part, so that as a result the support elements may be joined into a stable joint structure having a compact construction. However, this construction has the disadvantage that it requires a further component in the form of the connecting part to connect the support elements, which leads to an undesired increase of the total weight of the support frame.
A support frame for vehicles which comprises multiple assemblies based on hollow profiles is described in EP 0 568 251 B1. The hollow profiles are joined to one another via joint structures of different types in straight or angled positions, preferably perpendicular positions. The connection of profiles positioned perpendicularly to one another, such as the join between the B-column and side sillboard, is implemented via a T-shaped joint structure.
According to one embodiment of such a T-joint, a first hollow profile having a rectangular cross-section has two sections, each bent over by 90° and aligned with one another, having a C-shaped cross-section at one end, on which a second profile may be laid and welded thereto. The three-dimensional frame structure is implemented using two-dimensionally produced joint structures. A three-dimensional joint structure, i.e., the mutual connection of hollow profiles extending in three spatial directions at one point, is not provided in this case.
A joint structure similar to the above-mentioned embodiment of a T-joint is known from DE 37 26 079 A1. In this publication, a door frame construction for utility vehicles, particularly buses, is described. The central component of this construction is a T-joint structure for joining two hollow profiles perpendicularly to one another as components of the door frame. In this case, one of the hollow profiles is cut out lengthwise on diametrically opposing lateral surfaces on its end facing toward the other profile in such a way that two U-shaped attachment parts result, which may be deformed to a desired transition contour and laid on the profile to be attached. Since the door frame is a purely two-dimensional construction, no three-dimensional joint structures are implemented in this case either.
Furthermore, in an application known from practice, hollow profiles bent through hydroforming technology, which have a favorable weight because of the lack of weld flanges, are used to produce a three-dimensional joint structure. However, it has been shown to be problematic in this case that it is not possible to go below a minimum bending radius, so that use in vehicle body regions having tight construction space often does not come into consideration and, in addition, existing weight savings potential remains unused.
Finally, a three-dimensional joint structure comprising two hollow profiles, particularly having a square cross-section, is described in U.S. Pat. No. 1,972,309. To manufacture this joint structure, the first hollow profile is cut out over a specific length except for one remaining side and this side is bent around one of the lengthwise edges of a second hollow profile of identical cross-section positioned perpendicularly to the first hollow profile. The length of the cutout corresponds in this case to twice the edge distance of the hollow profiles, so that the bent side and the ends of the first profile adjoining the cutout completely enclose the four sides of the second hollow profile and press against them in a form-fitting way at the same time. According to an alternative design, the first hollow profile is notched along its four edges over the length cited and cut through centrally around its circumference on three sides in relation to this lengthwise cut. The regions notched on three sides resulting on these sides are bent perpendicularly outward and subsequently the side of the first hollow profile which is not cut through is bent around one lengthwise edge of the second hollow profile in the way described above, the regions bent outward pressing against two of the four sides of the second hollow profile as flanges.
A joint structure constructed in this way provides a high degree of rigidity, but is not variable in regard to the usable profile cross-sections. The length of the cutout and/or the notch of the lengthwise edges must be tailored precisely to the cross-sectional dimensions of the second hollow profile, in order to fulfill the requirement of a form fit, which is necessary for sufficient stability.